1. Field of the Invention
The present invention relates to a process for production of photoconductive cadmium sulfide, in particularly, to a process for production of photoconductive cadmium sulfide having high crystallinity, uniformity, and singleness.
2. Description of the Prior Art
Heretofore, photoconductive cadmium sulfide (CdS) used typically for electrophotografic material has most generally produced by a process which comprises precipitating cadmium sulfide particles by reaction of hydrogen sulfide with water-soluble salts of cadmium such as cadmium sulfate, cadmium chloride, and the like, and firing the resulting cadmium sulfide particles at a high temperature in order to add impurity to them. In other words, photoconductive cadmium sulfide are generally prepared by mixing cadmium sulfide particles with activating agents such as CuCl.sub.2, CuSO.sub.4, and the like, and flux such as CdCl.sub.2, ZnCl.sub.2, and the like, followed by firing so that cadmium sulfide is doped with Cu, Cl, etc.
However, in the above-mentioned conventional process, CdS prepared through the firing step has a number of defects in the vicinity of surface thereof upon precipitating.
Since the surface defects act as trapping level for photocarriers, photomemory of CdS increases, namely, photoresponse rate thereof is slowed down. When a photoconductive member prepared by use of such CdS is used for high-speed copying machine, electrostatic contrast between light portion and dark portion is insufficient.
Further, CdS particles prepared by the above-mentioned process are comprised of secondary particles, namely, strong aggregates formed by aggregating particles. Such secondary particles are comprised of conglomerates in which primary particles are three-dimentionally aggregated, and plates in which primary particles are two-dimentionally aggregated. The size of the large secondary particles ranges from ten and severl microns to several tens microns.
A photoconductive member prepared by use of CdS containing a number of such large size particules has an inferior surface and produces rough images which are insufficient in resolving power. In addition, when an insulating layer is provided on the above-mentioned photoconductive member, the insulating layer can insufficiently penetrate into the CdS layer. Therefore, it is difficult to prepare an excellent photoconductive member.